Gas turbines comprise a casing for housing a compressor section, combustion section and turbine section. The compressor section comprises an inlet end and an outlet end. The combustion section comprises an inlet end and a combustor transition. The combustor transition is proximate the discharge end of the combustion section and comprises a wall that defines a flow channel that directs the working fluid into the turbine inlet end.
A supply of air is compressed in the compressor section and directed into the combustion section. The compressed air enters the combustion inlet and is mixed with fuel. The air/fuel mixture is then combusted to produce high temperature and high pressure gas. This gas is then ejected past the combustor transition and injected into the turbine section to run the turbine.
Gas is forced through the blades of a gas turbine to run the turbine and produce electricity by causing the rotor to drive a generator. The blades of a turbine, as well as the blades in the compressor section of a turbine, typically comprise an airfoil, a platform, a shank and a root that fits into a complementary-shaped groove formed in the periphery of a rotor disc, which itself is located on the periphery of the rotor.
The airfoil portion of the blade is the distal portion of the blade that translates the axial flow of the gas to rotor rotation. Moving radially inward, the platform is the portion of the blade that rests on the outer surface of the rotor disc. The shank is the portion that extends down into the rotor disc from the platform and usually has a narrower cross-section than that of the platform. The root is the bottom portion of the blade that has a jagged or dovetail shape so as to fit securely within the groove of the rotor disc, which has a correspondingly complementary shape to that of the blade root.
During the operation of a gas turbine, the working gas can leak through gaps between the turbine blade roots and the corresponding grooves of a rotor disc. This yields a reduction in working gas to turn the turbine blades, thereby reducing the efficiency of the turbine section. Likewise, air in the compressor section of a gas turbine can leak through these same gaps. Thus, not all of the air entering the compressor is compressed, resulting in a decrease in efficiency of the compressor section. Leakage occurring in the compressor section of the turbine section reduces the efficiency of the gas turbine.
To prevent any leakage between the turbine blade roots and the corresponding grooves of a rotor disc, those skilled in the art have utilized several methods to seal this space. A common technique, during turbine assembly, is to affix a sealing device to the blade root and then mount the blade in the corresponding groove of the rotor disc. One such sealing method, disclosed in U.S. Pat. No. 5,558,500, is to affix an elastomeric seal made of silicone rubber to a portion of a blade root and then mount the blade root in the groove of a compressor rotor disc. This technique, as well as other prior art techniques, however, require sealing the gaps prior to mounting the turbine blades onto a rotor disc.
Therefore, to seal the gaps between turbine blade roots and corresponding grooves on a rotor disc of a working gas turbine, prior art sealing techniques require disassembly of the turbine. These prior art sealing procedures result in significant downtime of the turbine at a significant cost to the operator or customer. It is thus desirable to provide a sealing technique for retrofit application, allowing for sealing the gaps between turbine blade roots and corresponding grooves of a rotor disc while not requiring disassembly of any components of the gas turbine.